The present applicant's WO 98/17927 discloses a mechanical variable speed transmission having interconnected outer and inner differential gear trains for differentially driving two axles. The present applicant's WO 99/61820 discloses a hydraulic transmission connected in parallel to the compound differential of WO 98/17927 for controlling the torque/speed ratio of the two axles. The disclosures of WO 98/17927 and WO 99/61820 are incorporated herein by reference.
It is desirable to provide a hydromechanical variable speed transmission which is compact, clutchless, efficient, reliable and easy to manufacture.